Brent, I'm sure the repair bill will be hard to swallow... but knowing that you should never again have a cooling system issue in your coach will be $ well spent. And much cheaper than a cracked head or something major from running too hot for too long.
Since you're fillin' & flushin' anyways, you should look into DD's Power Cool Plus... said to be a 600,000 mile coolant change when used in highway service (even if it's fractionally fewer miles in RV service, it's likely to outlive the coach and/or driver). http://www.detroitdiesel.com/partsandservice/parts/performanceparts.aspx
Whatever you do, be sure and follow DD's recommendations on coolant: http://www.detroitdiesel.com/Public/brochures/7SE298.pdf
Please keep us posted. I'm anxious to see how much of an improvement the radiator makes. I'm hoping a LOT.